Quick freeze control



c; B. sPANGENBl-:RG '2,261,593

QUAICK FREEZE CONTROL Nov.l 4, 1941.

Filed Oct. 17, 1938 Patented Nov. 4, 1941 QUICK FREEZE CONTROL CharlesB. Spangenberg, Minneapolis, Minn., as"- signor to Minneapolis-HoneywellRegulator Company, Minneapolis, Minn., a corporation of DelawareApplication October 17, 1938, Serial No. 235,325

12 Claims.

This invention relates to a control system for a refrigerating apparatushaving evaporator means for cooling a'space and for freezing asubstance.

'I'he prime object of this invention is to provide a control system forsuch a refrigerating apparatus wherein the refrigerating apparatus isnormally controlled by a thermostat to maintain desired temperatureconditions within the space and wherein the refrigerating apparatus maybe operated independently of the thermostat until the suction pressuredecreases to a predetermined low value indicating that the evaporatormeans has frozen the substance. When this occurs the refrigeratingapparatus is then returned'to the normal c ontrol by the thermostat.

Another object of this invention is to provide in combination with theabove arrangement means for stopping operation of the'reirigeratingapparatus when the head pressure becomes excessive.

Still another object of this invention is to provide in combination withthe above arrangement means for preventing starting of the refrigeratingapparatus by the thermostat until the head pressure decreases to apredetermined low value and the suction pressure increases to apredetermined high value whereby the starting load on the compressor isdecreased to aminimum and compressor I1.

a liquid line 22'into the evaporator I3 under the control of anexpansion valve (not shown).

Evaporated refrigerant is withdrawn from the evaporator I3 throughasuction line 23 by the A fan 24 operated by a motor 25 may be utilizedfor cooling the condenser 20. Since the arrangement thus far describedis conventional in the art a further descriptionv thereof is notconsidered necessary, it being suilicient to state that when thecompressor I1 is operating a cooling action is performed by theevaporator I3.

The operation of thepcompreyssor I1 and the condenser fan 24 iscontrolled. by a relay or starter generally designatedl at 21. 4Therelay or starter 21 is in turn controlledby a temperature responsivecontroller 28 responsive to 4the temperature within the fixture I0, asuction pressure responsive controller 29 responsive to the pressure o'nthe low pressure side of the refrigerating apparatus and a head pressureresponsive controller 30 responsive to the pressure on the high pressureside of the refrigerating apparatus. The

controllers 28, 29, and 30 acting in conjunction with the relay orstarter 21 operate to start the compressor I1 and the fan 24 only whenthe temperature within the xture I0 increases to a predetermined highvalue, the pressure on the low whereby automatic defrosting of theevaporator l novel manner in which the above sequences of operation areobtained.

For a more thorough understanding of this invention reference is made tothe accompanying drawing in which is diagrammatically disclosed thepreferred form of this invention.

A iixture to be cooled may take the form of a cabinet or box designatedat I0 having a storage compartment II and a cooling compartment I2.Located within the cooling compartment I2 is an evaporator I3 providedwith a plurality of trays I4 in which a substance such as water or aconfection may be placed to be frozen. A drip pan I5 collects condensatefrom. the evaporator I3 during the Adefrosting cycle.

Refrigerant is supplied to and withdrawn from the evaporator I3 by meansof a refrigerating apparatus generally vdesignated at I6 which maycomprise a compressor I1 operatedby an electric motor I8. Compressedrefrigerant flows from the compressor I1 through a high pressure line I9into a condenser 20 andthe condensed refrigerant is 'collected in areceiver 2I. Liquid reirigerant'iiows from the receiver 2| throughpressure side of the refrigerating apparatus increases to apredetermined high value and the pressure on the high pressure side ofthe refrigerating apparatus decreases to a predetermined low valueandalso operate to maintain the compressor I1 and the fan 24 in operationuntil either the temperature in the fixture I0 decreases to apredetermined low value, or the pressure on the low pressure side of therefrigerating apparatus decreases to a predetermined low value or thepressure on the high pressure side of theI refrigerating apparatusincreases to a predetermined high value. AA manually operated controllergenerally designated at 3| is utilized for starting the compressor I1and the fan 24 independently of the temperature responsive controller 28to maintain the compressor I1 and `fan 24 in operation until thepressure on the lowipressure side of the refrigerating apparatusdecreases to the predetermined low value or the pressure on the highpressure side of theV refrigerating apparatus increases to thepredetermined high value for the purpose of quickly freezing thesubstance in the trays I4.

'Ihe relay or starter 21 may comprise a core 33 carrying an operatingcoil 34 and an armature 35 pivoted by a pin 36 to the core 33. Thearmature 35 carries in an insulated manner a contact a1 adapted. toengagy a contact as and also carries in an insulated manner contacts 3919v and 88 back to the other line wire 69. Comand 48 adapted to engagestationary contacts 4| and 42. Wliexrthe operating'coil 34 is energizedthe armature 35 is attracted to move the a circuit from the line wire 68through wires 8| The amature 35 also carries a bracket 43 the` I purposeof which will be pointed out m'ore fully hereafter.

'I'he temperature responsive controller 28 may comprise a bellows 45charged with a volatile fluid for operating a lever 46 against theaction of an .adjustable tension spring 41 which in turn operates amercury switch 48. For purposes of illustration it is assumed that theparts are so arranged that when the temperature within the fixture I8increases to 42, the mercury switch 48 is tilted to a closed position,and when the temperature decreases to 40, the mercury switch 48 is4tilted to an open position, as shown.'

The suction pressure responsive controller 29 may comprise a bellows 58connected by a pipe 5|* to the suction pressure line 23 for operating alever 52 against the action of an adjustable tension spring 53. 'I'helever 52 carries irran insulated manner contacts 54 and 55 which areadapted to engage sequentially adjustable -stationary contacts-56 and51, respectively.r vFor purposes of illustration it is assumed that whenthe pressure on the low pressure side of the refrigerating apparatusincreases to lbs., the contact 54 engages the contact'56 and when thepressure increases to 32 lbs. the contact 55 engages the contact 51.Upon a decrease in suction pressure the 'contact 55 first disengages thecontact 51 at 32 lbs. and then the contact 54 disengages the contact 56at 10 lbs.

The head pressure responsive controller 38 may comprise a bellows, 59connected by a pipe 68 to the high pressure line I9 for operating alever -6I against the action of an adjustable tension spring 62. Thelever 6| carries in an insulated manner contacts 63 and` 64 which areadapted to engage sequentially adjustable stationary contacts 65 and 66,respectively. For purposes of illustration it is assumed that as thepressure on the high pressure side of the refrigerating apparatusdecreases, the contact 63 engages the contact 65 at 190 lbs. and thecontact 64 engages the contact 66 at 140 lbs. Conversely, upon anincrease in head pressure the contact 64 first disengages the contact 66at 140 lbs. and then the contact 63 disengages theV contact 65 at 190lbs.

Power is supplied to the compressor motor I8, to the fan motor 25 and tothe control system by means of line wires 68 and 69 leading from somesource of power (not shown).

When the temperature within the xture I8 increases to 42 to close themercury switch 48 the pressure on the low pressure side of therefrigerating apparatus increases to 32 lbs. to close the contacts 54,56 and 55, 51 and the pressure 'on the high pressure sideof therefrigerating apparatus decreases to 140 lbs. to close the contacts 63,65 and 64, 66, a starting circuit is completed from the line wire 68throughwire 18, contacts 65 and 63, wire 1I, contacts'54 and 56, wires12 and 13, mercury switch 48, wires 14 and 15, contacts 51 and 55, wire16, contacts 64 and 66, wires 11 and 18, operating coil 34, and wirespressure responsive controller 38.

`pletion of this circuit energizes the operating coil 34 to pull in therelay or starter 21.

Movement of the contact 48 into engagement vwithlthe contact 42completes a circuit from the line wire 68 through wires 8| and 82,contacts 48 and 42, wire 83, compressor motor I6, and wire 8'4- back to'the line wire 69 to operate the compressor .1. Movement of the contact39 into engagement with the contact 4I completes and 85, contacts 39 and4I, wire 86, fan motor 25, and wires 81 and 88 back to the line wire 69to operate the condenser fan 24. Accordingly when the relay or starter21 is pulled in the compressor I1 and the `fan 24 areplaced inoperation.

Movement of the contact 31 of the relay or starter 21 into engagementwith the contact 38 completes a maintaining circuit for the operatingcoil 34 which is independent of the contacts 55 and 51 of the suctionpressure responsive controller 29 and thecontacts 64 and 66 of the head'I'his maintaining circuit may be traced from the line wire 68 throughwire 18, contacts 65 and 63, wire 1|, -contacts 54 and 56, Wires 12 and13, mercury switch 48, wires 14,89, and 98, contacts 31 and 38, wires 9|and 18, operating coil 34, and wires 19 and 88 back to the other linewire 69. Completion of this circuit maintains the operating coil 34yenergized until either the temperature within the xture I8 decreases to40 to open the pressor I1 and the fan 24 are placed in operation onlywhen the temperature within the ilxture I8 increases to 42, the suctionpressure increases to 32 lbs. and the head pressure decreases to 140lbs. and is maintained in operation until either the temperature in theiixture I8 decreases to 40, or the suction pressure decreases to 10 lbs.or the head pressure increases to 190 lbs. Accordingly the temperaturewithin the fixture I8 is maintained between 40 and 42. Since thecompressor I1 cannot be started until the pressure on the low pressureside of the refrigerating apparatus increases to, 32 lbs. defrosting ofthe exterior surface of the evaporator I3 is afforded during each cycle'of operation of the refrigerating apparatus. Since it is impossible tostart the compressor I 1 until the head pressure de-` creases to lbs.the starting load on the compressor motor `|8 .is decreased to aminimum. Since the compressor I1 can be stopped when either the suctionpressuredecreases to 10 lbs. or the head pressure increases to lbs. safeoperation ofthe compressor is afforded.

The manuallyoperatedcontrol means 3| may comprise a rod 95 slidablymounted in a suitable support 96. A compression spring 98 locatedbetween the support 96 and a suitable operating knob 91 maintains acollar 99, mounted on the rod 95, against the support 96. In otherwords, the rod 95 is at all times urged to the right by the compressionspring 98. The rod 95 carries a latch |88 which isadapted to engage theVto engage a contact |04. Contacts-IM and The vcontrol o f the uponreturned to the normal control circuits in |03 are so arranged that theyare sequentially closed upon left hand movement of the rod 95,` thecontact IOI engaging i'lrst the contact |02 and then the contact 03engaging the contact |04. When the relay or starter 21 ls pulled infollowing left hand movement of the rod 95, the bracket 43 engages thelatch |00 to hold the contact IOI in engagement with the contact |02 butallowing the contact |03 to separate from the contact |04. When thebracket 43 disengages the latch upon dropping out of the relay orstarter, the spring 98 moves the rod 95 to the right, as shown in thedrawing.

Assume now that the pressure on the high pressure side of therefrigerating apparatus is below/190 lbs. to cause the contacts 63 and65 to engage and that the pressure on the low pressure side of therefrigerating apparatus is above 1bs.,to cause contacts 54 and 56 toengage. If now the operator pushes the button 91 to overcome the spring98, the contact IOI first engages the contact |02, and when the contactI 03 engages the contact |04 a starting circuit for the operating coil34 of the relay or starter 21 is completed, this starting circuit beingtraced from the line wire 68 through Wire 10, contacts 65 and 63, wire1I, contacts 54 and 56, wires 12, |06, and |01, contacts |03 and |04,wires |08, 9|, and 18, operating coil 34 and wires 19 and 80 back to theline wire 69. Completion of this circuit energizes the operating 'coil34 'to pullin the relay or starter 21 which causes the bracket 43 tolatch behind the latch' |00. After relay or .starter 21 has thus beenpulled in to start the compressor I1 and fan 24, theeope'rator releasesthe button 91 .but the latch |00 is caught by the bracket 43 to hold thecontact |0I in engagement with the contact |02. A maintaining circuit iscompleted through the contacts IOI and |02 which may be traced from theline wire 68 through wire 10, contacts 65 and 63, wire 1I, contacts 54and 56, wires 12, |06, and IIO, contacts IOI and |02, wire 90, contacts31 and 38, wires 9| and 18, operating coll 34 and wires 19 and 80 backtothe otherline wire 69. Completion of `this circuit maintains theoperating coil 34 energized and the compressor and fan in operationuntil either the suction pressure decreases to 10 lbs. to separate thecontacts 54 and ,56 or the pressure on the high pressure side increasesto 190 lbs. to separate the contacts 63 and 65. When either of thesecontingencies occur therelay or starter 21 drops out and the bracket 43is released from the latch |00 Whereupon the contacts IOI and |02 areseparated.

relay or starter 21 is therecluding the temperature responsivecontroller 28. It is here noted that the auxiliary circuit including thecontactsf,|03 land |04 is in parallel i with the mercury switch 48 ofthe` temperature responsive controller, the contacts 64 and 66 of lthehead pressure responsive controller 30 and the contacts 55 and 51 of thesuction pressure responsive Vcontroller y29 so that the relay or starter21 and hence the compressor I1 may be 'placed in operation independentlyof the temperature of the fixture I0 and the cut-in pres- ,sures on thehighV pressure side and the low pressure side of the4v refrigeratingapparatus. In

other words, by manual manipulation of the controller 3I'the compressorI1`may be started regardless of the temperature within the enclosure I0providing the suction pressure is not exces- .sively low and the headpressure is not excessively high. It is also here noted that theauxiliary maintaining circuit including the contacts IOI and I 02 is inparallel with the mercury switch 48 of the temperatureS responsivecontroller 28 so that the compressor I1 may be maintained in operationregardless of the temperature within the fixture I0 until such time asthe suction pressure decreases to 10 lbs. or the head pressure increasesto lbs. By reason of the auxiliarystarting and maintaining circuits thecompressor I1 may be maintained in continuous operation until thesuction pressure decreases to the cut-out value of v1I) lbs. at whichtime freezing ofthe substance in the trays I4 is assured thereby givinga very rapid freezing action. After the compressor has been stopped bythe suction pressure controller 29, the manualcontroller 3| is renderedinoperative so that the compressor I1 is subsequently placed under thenormal control including the temperature responsive controller 28.

From the above it is seen that I have provided a control arrangement fora refrigerating apparatus having evaporator means for cooling a spaceand for freezing a substance wherein the compressor is operated undernormal control to maintain desired temperature conditions within a spaceand still provide intermittent defrosting of the evaporator means,wherein the compressor may be operated independently of the temperatureresponsive controller until the suction-pressure decreases to apredetermined .low value for quickly freezing the substance and whereinthe compressor is returned to the normal control by the temperature`responsive controller after the substance has been frozen.

Although for purposes of illustration one form of this inventionhas beendisclosed other forms thereof may become apparent to those skilled inthe art upon reference to this disclosure and therefore this inventionis to be limited only by the scope of the appended claims and the priorart.

I claim as my invention:

1. In a refrigeration system including a refrigerating apparatus havinga compressor and evaporator means-for cooling a space and for thecontrol yof the compressor to the temperature responsive control means.

2. In a refrigeration system including a re-` frigerating apparatushaving a compressor and evaporator means for vcooling a space and forfreezing a substance, the combination with saidapparatus of,controlmeans responsive to the temperature of the space for normallycontrolling the compressor to maintain the space temperature Withindesired limits, control means responsive to the pressure on the lowpressure side of the refrigerating apparatus for always stoppingoperation of the compressor when the l' pressuredecreases ltofa.predetermined low value, control meansresponsive to the pressure on thehigh pressure side of theyrefri'gerating apparatus for alwaysstoppingoperationof thecompressor when the pressure increases to a predetermined.high value, and means for operating the com- -pressor independently ofthe temperature responsive control means .until the compressor is rfrigerating apparatus having a compressor and evaporator means forcooling a space and for freezing a substance, the combination withsaidapparatus of, control means responsive to the temperature of thespace, control means respons'ive to the pressure on the low pressureside of the refrigerating apparatus, mechanism controlled by bothcontrol means to start the compressor when the space temperatureincreases to ananas determined high value and the pressure on the highpressure side decreases to a predetermined low value and to stop thecompressor when either a predetermined .high value and the pressure onthe low pressure side increases to a predetermined high value and tostopgthe compressor when either the space temperature decreases to apredetermined low value or the pressure on the low pressure sidedecreases to a predetermined low value, and means operatively associatedwith -said pressure responsive control means for also controlling saidmechanism to operate the compressor independently of the temperatureresponsive control means until the pressure responsive control meansstops the compressor for quickly freezing the substance.

4. In a refrigeration system including a refrigerating apparatus havinga compressor and evaporator means for cooling a space and for freezing asubstance, the combination with said apparatus of, control meansresponsive .to the temperature of the space, control means responsive tothe pressure on the low pressure side of the` refrigerating apparatus,mechanism controlled by both control means .to start the compressor whenthe space temperature increases to a predetermined high value and thepressure on the low pressure side increases to a predetermined highvalue and to stop the Acompressor when either the space temperaturedecreases to a predetermined low value or the pressure on `the lowpressure side decreases to a predetermined low value, and meansoperatively associated with said pressure responsive control means foralso controlling said mechanism to start the compressorl even though thelpressure and temperature have not increased to the starting values andfor continuing the compressor in operation until the pressure decreasesto the stopping value for quicklyfi'eezing ,the sub` stance. I

5. In a refrigeration system` including a refrigerating apparatus havinga compressor andI evaporator means for cooling a space and for-`freezingr a substance, the combination with .said

apparatus f, control means responsive to the temperature of the space,control means responsive to the'pressure on the low pressure side of.the refrigerating apparatus, control means responsive to the pressure onthe high pressure side ci the reir'igerating apparatus, mechanism thespace temperature decreases to a predetermined low value or the pressureon the low pressure side decreases toa predetermined low'value or thepressure on the highV pressure side increases to a predetermined highvalue, and means operatively associated with said pressure responsivecontrol means for also controlling said mechanism to operate thecompressor independently of the temperature responsive control meansuntil either the pressure on the low pressure sidedecreases to thepredetermined .low value for quickly freezing the substance or until thepressure on the high pressure side increases to the predetermined highvalue.

, 6. In a refrigeration system including a re-V frigerating apparatushaving an electrically operated compressor and evaporator means forcooling a space and for freezing a substance, the combination with saidapparatus of, a relay for operating the compressor when energized, firstswitch means, means responsive to the temperature of the space foroperating the first switch means, means for completing a circuit throughthe first switch means and the relay for operating the compressor tomaintain desired temperatures within the space, second switch means,means responsive to the pressure on the low pressure side of therefrigerating apparatus for opening the second switch means when thepressure decreases to a predetermined low value, normally open switchmeans, means for closing the normally open switch means and for holdingthe normally open switch means closed as long as the relay is energized,and means for completing a circuit through the second switch means, thenormally open switch means and the relay for operating the compressorindependently of the rst switch means until the pressure on the lowpres-l sure -side decreases to the predetermined low value to freezequickly thesubstance.

7. In a refrigeration system including a refrigerating apparatus havingan electrically operated compressor and evaporator means for cooling aspace and for. freezing a substance, the combination with said apparatusof, a relay for operating the compressor when energized, first switchmeans, means responsive .to the temperature of the space for operatingthe first switch means. second switch means, means responsive to the vpressure on the low pressure side of' the refrigcontro' ledby all ofsaid'control means to start the' compressorwhen the space temperatureincreases to a predetermined high value, the pres- 'sure on the lowpressure side increases to apre- -erating apparatus for opening thesecond switch means when the pressure decreases to a predetermined lowvalue, normally open switch means, means for closing the normally openswitch means and for holding the normally open switch means closed aslong as the relay is energized, means `for completing a circuit throughthe first and second switch means and the relay for operating .thecompressor to maintain desired temperatures within the space and to stopthe compressor when the pressure on the low pressure side decreases vtothe predetermined low value, and`means for completing a circuit throughthe second switch means,'the normally open switch means and the relayfor operating the compressor independently of the first switch meansuntil the pressure on the low pressure, side decreases to thepredetermined low value to freeze quickly the substance. 8. In arefrigeration system includingr a refrigerating apparatus having anelectrically operated compressor and evaporator means for cooling aspace and for freezing a substance, the combination with said apparatusof, a relay for operating the compressor when energized, rst switchmeans, means responsive to the temperature of th,- space for operatingthe first switch means, second switch means, me'ans responsive to thepressure on the low pressure side of the refrigerating apparatus foropening the second switch means when the pressure decreases to apredetermined low value, third switch means, means responsive to thepressure on the high pressure side of the refrigerating apparatus foropening the third switch means when the pressure increases to apredetermined high value, normally open switch means, means for closingthe normally open switch means and for holding the normally open switchmeans closed as long as the relay is energized, means for completing acircuit through the rst, second and `third switch means and the relayfor operating the compressor to maintain desired temperatures within thespace and to stop the compressor when either the pressure on the lowpressure side decreases to the predetermined low value or the pressureon the high pressure side increases to the predetermined high value, andmeans for completing a circuit through the second and third switchmeans, the normally open switch means and the relay for operating thecompressor independently of the rst switch means until either thepressure on the low pressure side decreases to the predetermined lowvalue or the pressure on the high pressure side increases to thepredetermined high value to freeze quickly the substance;

9. In a refrigeration system including a refrigerating apparatus havingan electrically operated compressor and evaporator means for cooling aspace and for freezing a substance, the combination with said apparatusof, a relay including an operating coil and a load switch andmaintaining switch which are closed upon energization of the operatingcoil, means for completing a circuit through the load switch and theelectrically operated compressor for operating the compressor when theoperating coil is energized, first switch means, means responsive to thetemperature of the space for closing and opening the first switch meansas the space temperature increases above or decreases to respectively adesired value, second and third switch means, means responsive to thepressure on the low pressure side of the refrigerating apparatus forclosing the second mally open switch means, the third switch means andthe operating coil to maintain the compressor in operation until thepressure on the l'ow pressure side decreases to the predetermined lowvalue to freeze quickly the substance.

10. In a refrigeration system including a refrigerating apparatus havingan electrically operated compressor and evaporator means for gization ofthe operating coil, means for completing a circuit through the loadswitch and the electrically operated compressor for operating thecompressor when the operating coil is energized, first switch means,means responsive to the temperature of the spacevfor closing and openingthe rst switch means as the space temperature increases above ordecreases to respectively a desired value, second and third switchmeans, means responsive to the pressure on the low pressure side of therefrigeratingapparatus for closing the second switch means when thepressure increases to a predetermined high value and for opening thethird switch means when the pressure decreases to a predetermined lowvalue, fourth and fth switch means, means for biasing the fourth andfifth switch means toward an open position, means forovercoming thebiasing means to close the fourth and fifth switch means, means operatedby said operating coil to hold the fifth switch means closed against theaction of the basing means as long as the operating coil is energized,means for completing a starting circuit through the first and secondswitch means and the operating coil to start the compressor when thespace temperature increases above the desired value and the pressure onthe low pressure side increases to the prede- Y termined high value,means for completing a maintaining circuit through the firstl and thirdswitch means, the maintaining switch and the operating coil to maintainthe compressor in operation until the space temperature decreases to thedesired value or the pressure on the low pressure side decreases to thepredetermined low value, means for completing an auxiliary startingcircuit through the fourthswitch means and the operating coil to startthe compressor independently of the rst switch means, and means switchmeans when the pressure increases to a I predetermined high value andfor opening the third switch-means when the pressure decreases to apredetermined low value, normally open switch means, means for closingthe normally open switch means and for holding the normally open switchmeans closed as long as the operating coil is energized, means forcompleting a starting circuit through the rst and second switch meansand the operating coil to start the compressor,

when the space temperature increases above the desired value and thepressure on the low pres` sure side increases to the predetermined highvalue, means for completing a maintaining circuit through the iirst andthird switch means, the maintaining switch and the operating coil tomaintain the compressor in operation until the space temperaturedecreases to the desired value or the pressure on the low pressure sidedecreases to 'the predetermined low value, and means for completing anauxiliary circuit through the norfor completing an auxiliary maintainingcircuit through the third and fth switch means, the maintainnig switchand the operating coilto maintain the compressor in operationindependently of the rst switch means until the pressure on the lowpressureV side decreases to the predetermined low value to freezequickly the substance.

11. In @refrigeration system including a refrigerating apparatus havingan electrically operated compressor and evaporator means for cooling aspace and for freezing a substance, the combination with said apparatusof, a relay including an operating coil and aload switch and maintainingswitch which are closed upon energization of the operating coil, meansfor completing a circuit through the load switch and the i means, meansresponsive to the pressurefon the low pressure side of the.refrigerating apparatusfor closing the second switch meanswhen thepressure increases yto a predetermined Vhigh value and for opening thethird switch means when the pressure decreases, to a predetermined lowvalue, fourth' and fifth switch means, means for biasing the fourth andfifth switch means toward an open position, means for overcoming thebiasing means to close the fourth and fifth switch means, means operatedby said operating coil to hold the fifth switch means closed against theaction of the biasing means as long as the operating coil is energized,means for completing a starting` circuit through the ilrst and secondcompressor when the space temperature .increases above the desired valueand the pressure on the low pressure side increases to the prede.termined high value, means for completing a maintaining circuit throughthe first and third switch means, theY maintaining switch and theoperating coil to maintain the compressor in op- .eration until thespace temperature decreases to the desired value or the pressure on thelow pressure side decreases to the predetermined low value, means forcompleting an auxiliary starting circuit through the third and fourthswitch means and the operating coil to start the com` pressorindependently of the first switch means,

-dependently' ofthe first switch means until the switch means and theoperating coil to start the pressureon the low pressure side decreasesto the predetermined -low value to freeze quickly the substance.

12. In a refrigeration system including a refrigerating apparatus havinganelectricallyL 01,11-,

erated compressor and evaporator means for cooling a space and forfreezing a substance, the

ycombination with said apparatus of, a r'elay causing closure of saidrelay operated switch upon operation ofthe manual operator, a manualswitch moved to closed position by said manual operator when sooperated, mechanical connections controlled by said relay mechanism forholding said manual switch closed after release of said manual operatorso long as the relay operated switch is in closed position, a'circuitfor Y the operating means of said relay controlled by` and m'eans forcompleting an auxiliary main-jf coil to maintain the compressor inoperatioxrinvnamed circuit.

said manually operated switch, and means responsive to a conditionindicating that the substance has been frozen for interrupting said lastCHaRLEs B. SPANGENBERQ.

